A significant problem in studying the pharmacologic basis of narcosis is that no satisfactory means has yet been found, in the intact anesthetized animal, to assess quantitatively the degree of anesthesia over a range of administered concentrations. The best method yet devised is to measure the ED50 in terms of lack of withdrawal response to a noxious stimulus. This, coupled with the LD50, gives only two points on a dose-response curve which varies from slight alterations of consciousness to death. We propose to study escape and avoidance behavior in response to electric shock in the goldfish, a species that has been shown to be useful in behavioral research, and whose responses to anesthesia parallel those of man. Preliminary investigatton in our laboratory suggest that escape latency from supramaximal shock is a sensitive and reproducible index of anesthetic effect up to the point at which immobility occurs, enabling the construction of dose-response curves over the continuum from the normal awake state to the onset of narcosis. Such information should enhance investigation of additivity and parallelism among anesthetics and provide a sounder basis for studying mechanisms of anesthetic action.